A diary is the one thing you write that is meant for nobody. Most journal apps still route it through a company: an account to open, a cloud to sync to, a subscription to keep the door open. Some of them encrypt it well. None of them can match a diary that never leaves your device in the first place.
Dash is an encrypted diary in that older sense. Entries are pages on your Mac or iPhone. Lock an entry and it is encrypted with AES-256-GCM; open it with your password, Touch ID or Face ID. Nothing is uploaded unless you turn on the optional end-to-end encrypted sync, and the Mac app is a one-time purchase.